湖南桃江稻瘟病菌遗传多样性分析及无毒基因的鉴定.

[Objective] The present paper aimed to clarify the genetic diversity and composition of non-toxic genes of Magnaporthe oryzae in Taojiang. [Method] Genetic diversity of 29 M. oryzae isolated and purified from several late rice varieties in Taojiang disease nursery was analyzed by 8 pairs of SSR primers. And nontoxic gene of 19 isolates were identified through 18 near-isogeniclines(NILs) whose resistance gene to blast were known. [Result]The results indicated that under the 0. 70 similarity coefficient and 0. 30 difference coefficient level, the total isolates of twenty-nine could be divided into seven genealogies. The dominant genealogy 1 contained 12 isolates, accounting for 41.3 % of the total isolates. The V genealogy contained 7 isolates, accounting for 24. 1 % of the total isolates. The other 5 genealogies contain 1 -3 isolates, accounting for 34.6 % of the total number of isolates. The pathogenic frequency (pathogenic frequency = the number of susceptible rice varieties / the number of total tested rice varieties x 100 %) ranged from 35 % to 75 % , and there were 3 strong pathogenic iso-lates (pathogenic frequency > 70 %) which accounted for 15. 7 % of the total isolates ;7 isolates were highly pathogenic (70 % > pathogenic frequency ^50 %) , accounting for 36. 8 % of the total isolates. Nine medium pathogenic isolates (50 % > pathogenic frequency ^20 %) , accounted for 47. 5 % of the total isolates, and the average pathogenic frequency of the tested isolates was 49.86 % . The virulence frequencies of 19 isolates to NILs (virulence frequencies = the number of isolatesto be tested the virulence with NILs / the number of all isolates x 100 %) were identified by avirulence gene, it was shown that more than 70 % of the virulent genes what with highly virulent were Pi-ks, Pi-ztand Pi-ta. The resistance gene whose virulence frequency was between 50 % and 70 % with medium virulence were pi-kp , pi-z5 , pi-t, pi-sh and Pi-5. The virulence frequency of the other resistance genes was less than 50 %. [Conclusion] The population of Pyricularia oryzae in Taojiang, Hunan province has abundant genetic diversity and complicated pathogenicity differentiation. The resistance genes Pi-3, Pi-i, Pi-11, Pi-19 and Pi-12 have excellent resistance to M. oryzae in Taojiang area and can be used in disease resistance breeding. [ABSTRACT FROM AUTHOR]